The conventional linear movement device includes a longitudinal rail unit and a movable member. The movable member and the rail unit each provide one row of rail. A series of rollers are located between the rails and the rollers are movable on the rails. The movable member provides a return path and two U-turn paths to each rail. The U-turn paths communicate with the return path, the entrance and exit of the rails to form a circulation path. The rollers re-enter the return path via the rail area and then enter the rail area via the return path. By this way, the rollers can move along the circulation path. The movable member then moves endlessly along the rails by the movement of the rollers.
In order to avoid impact between the rollers, the movable member provides a maintaining chain for the rollers. A series of maintaining blocks are located between the rollers and connected by a connection wire such that the maintaining blocks separate the rollers one by one to avoid impact between the rollers. The rollers therefore are maintained a certain distance therebetween and move smoothly without impact.
The rolling members comprise balls and rollers, for the ball maintaining chain, JP05-052217 discloses a ball chain, Taiwan Patent I303696 discloses a rolling members maintaining chain, and Taiwan Patent I294497 discloses a linear rail maintaining member.
The maintaining chain usually needs secondary injection molding or secondary machining and assembling because of de-molding interference. The extra machining processes make the maintaining chain have an uneven surface which may affect the movement of the rolling members.
The applicant invents ball maintaining chain and a method for making ball maintaining chain and linear movement device disclosed in Taiwan Patent Application No. 201122262 which provides a mold set for the ball maintaining chain which is completed by only one injection molding. The invention further provides a method of inclined de-molding so as to eliminate the drawbacks of the conventional methods. The ball maintaining chain is a flat and elongate chain which has holes in the axial direction. There is a plate located between the adjacent holes, and each plate has a top block and a bottom block connected thereto. The top and bottom blocks are partially formed as a spherical surface so as to maintain the balls and guide the balls to move in the correct path.
Taiwan M334223 discloses a linear roller maintaining chain which has two flexible linking portions and multiple even-distanced separation blocks which are located between the linking portions. A room is defined between the two separation blocks and each block has two maintaining blocks. One of the maintaining blocks protrudes upward from the top surface and the adjacent maintaining block protrudes downward from the bottom surface. The respective distal ends of the protrusions are respectively inclined toward the room. Taiwan I288212 discloses a synchronized roller maintaining member and comprises two flexible linking portions and multiple even-distanced separation blocks which are located between the linking portions. A room is defined between the two separation blocks for receiving a roller. Each separation block is composed of two or more than two mainlining blocks. One of the maintaining blocks has a cylindrical maintaining portion and a flat extension portion on two sides thereof. The cylindrical maintaining portions and the flat extension portions on the same side of the maintaining blocks of the same separation block are located corresponding to each other. However, because of the specific shape of the maintaining blocks, there will be two de-molding seams visible on the maintaining block and the seams include surplus material which makes the products have higher defect rate.
Taiwan Patent No. 473595 shows that the roller maintaining chain is accommodated in the recesses defined by the separation plates. The guide belt cannot maintain the rollers which are maintained by the separation plates so that the rollers are not well positioned and tend to shake when in operation.
Taiwan M335587 discloses a synchronized connector for the rollers have two connection wires and multiple first maintaining members and second maintaining members. The first and second maintaining members are installed to the connection wires evenly, and a room is defined between the first maintaining members and between the second maintaining members so as to have lubricant received therein. However, in order to obtain the rooms, slider is used when de-molding and this means high manufacturing cost is involved.
JP2005-069444 discloses “Molding method for roller connection body and mold and molding device used in molding method”, wherein a fixed mold and a movable mold are used. The movable mold is de-molded along the top-inclined direction of the maintaining chain, and the resin made maintaining chain left on the fixed mold can be taken out removed by 25 pins extending from the fixed mold. However, the maintaining chain is pushed by the 25 pins in a bent form, instead of straight form. This may damage the maintaining chain.
The present invention intends to provide a roller maintaining chain which is an improvement based on Taiwan Patent Application No. 201122262 and the roller maintaining chain provides a proper maintaining force to the rollers located in the recesses in the chain and does not interfere the movement of the rollers. Furthermore, the method for making the roller maintaining chain that is de-molded in the inclined direction so that the maintaining chain can be obtain by one injection and this simplifies the process for making the roller maintaining chain. The problems of the surplus material and the uneven surface can be improved. In order to form the accommodating surface for maintaining the cylindrical rollers, avoid the de-molding interference, and have a flat surface on a portion of the accommodating surface, the present invention provides a linear movement device.